The arrival of foreign spruikers comes as the Federal Government's key investment policy maker, Ross Cameron, said their damage had so far been obscured by a booming property market.

"The you-know-what's going to more than hit the fan as the property market slows," Mr Cameron, the Parliamentary Secretary to the Treasurer, said in an interview.

Mr Allen was brought to Australia by a company associated with Ronnie Kagan, a former partner of Henry Kaye.

Denise Brailey, president of the Real Estate Consumers Association, said she and a Channel Seven cameraman were assaulted and manhandled by six security guards at a Robert Allen seminar on Tuesday night. Guards blocked their vehicle from leaving the premises, she said.

Both the ACCC and the Australian Securities and Investments Commission, the two key regulators under Mr Cameron's control, have said they would like to see a national property investment regulatory regime.

But Mr Cameron said consumers and investors needed to watch out for their own welfare rather than expect the Federal Government to regulate their safety.

He said property investments had been a state responsibility since colonial days and "there is no way of unscrambling Humpty Dumpty". The states would need to forgo funding if Canberra was to reconsider, he said.

Mr Cameron said Australians had paid a price for the "tendency for us to relax in the placental warmth of the embrace of the state".

He said his lassiez-faire philosophy made him an unusual choice as the Government's key consumer policy maker and he had probably been a "disappointment" to his masters.

But he said Prime Minister John Howard supported his inclination to leave property regulation to the states.

"The PM will say that if every time the states screw up we have to intervene, then why do we have them?"

Treasury believes an effective regime would require new laws and a new bureaucracy and could not simply be spliced into the existing financial services reform laws.

Leaders at the regulators and Treasurer say the states have so far botched efforts to present their case to Canberra - although there remains some hope. The issue of property regulation had not been brought before Cabinet, government sources said.